Santo Domingo, Dominican Republic - At least 13 people died and more than 6,000 were displaced due to the effects of Hurricane Gustav on the Caribbean island of Hispaniola, authorities in Haiti and the Dominican Republic said Wednesday.

Gustav made landfall on Haiti on Tuesday as a hurricane, but weakened and was downgraded to a tropical storm early Wednesday, with sustained winds of 95 kilometres per hour and higher gusts, the Miami-based US National Hurricane Centre said.

Heavy rain and squalls were still pummelling parts of Haiti, which shares the island with the Dominican Republic, the centre said.

The hurricane centre said the storm was expected to pass between Jamaica and the south-eastern coast of Cuba on Thursday and "could regain hurricane strength within the next day or two."

As it passed the Dominican Republic, it left eight people dead, in a mudslide that buried a home in Santo Domingo. Authorities said 5,425 people were displaced from their homes and more than 1,000 homes were damaged.

Five other people died in Haiti, where some 10 others were injured and over 1,000 families had to be evacuated from their homes.

Beginning early Wednesday, troops of the United Nations Stabilization Mission in Haiti (MINUSTAH) and Haitian Civil Protection officers were patrolling the impoverished nation to inspect affected areas and distribute water and food.

Both countries suffered damages to agriculture from strong winds and electric thunderstorms.

Gustav could dump 15 to 30 centimetres of rain over Hispaniola, eastern Cuba, Jamaica and the Cayman Islands. At 1500 GMT, it was located about 180 kilometres west of Port-au-Prince, Haiti, and 200 kilometres south-east of Guantanamo, Cuba.

US authorities warned residents to be prepared for a possible landfall in coming days, but noted it was too soon to know where the storm might make come ashore after crossing the Gulf of Mexico.

"We are continuing to monitor this storm as state government agencies, including the state police and the Louisiana National Guard, have been put on standby so we are ready to quickly respond if the storm heads our direction," Louisiana Governor Bobby Jindal said. Three years ago Hurricane Katrina devastated New Orleans and much of the Gulf Coast in the state and neighbouring Mississippi, leaving more than 1,800 people dead.

Tropical Storm Gustav had driven up the price of crude oil on fears it could impact oil platforms in the Gulf of Mexico, Bloomberg financial news reported.

Last week, Tropical Storm Fay left 11 people confirmed dead and some 50 missing and caused substantial damage to agriculture in Haiti and the Dominican Republic.

Gustav is the seventh storm in the current north-Atlantic hurricane season, and the third hurricane. The season officially ends at the end of November.